Device on rotary screen printing machines

ABSTRACT

A device on rotary screen printing machines for longitudinally tensioning the rotary screens. The screen holders of at least one machine side being adjustable in parallel to the rotary screen axis wherein an adjustable device for the movable screens is provided. The adjustable device comprising stopping means, the stopping means limiting the movement of the screen holder to a predetermined extent upon release.

United States Patent [56] References Cited UNITED STATES PATENTS 10/1958Leibenguth [72] Inventor WalterBolun Klrchbichl No. 143, Tyrol, Austria[21] AppLNo. 761,466

101/1271 l0l/l27.1 101/1271X 2,854,922- 3,39l,635 7/1968 Matheus......3,404,623 10/1968 Watkin..............,..l.......

[22] Filed Sept. 23, 1968 [45] Patented June 22, 1971 [32] PrioritySept. 27, 1967 1 1 FQll l IliiN PATENTS Canada Primary Examiner- RobertE. Pulfrey Assistant Examiner-Alan E. Kopecki Auamey- Wenderoth, Lind &Ponack Austria A 8757 ABSTRACTrA device on rotary screen longitudinallytensioning the rota m m R P. N E E R w m. n r A g T .m 0 w R n NSD 0W3,E15 m m vm E DM4 M D Km s .mmm hma u m i hh .m t .m n mm. ed a c 500 mIn ders of at least one machine side b th e rotary sc'reen axis whereinan adjustable device for the movable screens is provided. The adjustabledevice comprising stopping means, the stopping means limiting themovement of the screen holder to a predetermined extent upon release.

PATENTEU JUH22 I57;

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WALTER BOUM HMM X a! P ATTORNEY f5 PATENTED JUHZZ 19?:

SHEET 2 BF 2 WALTER 130] IM,

INVENTOR BYHJJIAM.ZLJ

ATTORNEY s DEVICE N ROTARY SCREEN PRINTING MACHINES This inventionrelates to a device on rotary screen printing machines forlongitudinally tensioning rotary screens, the screen holders of at leastone machine side being adjustable in parallel to the rotary screen axis.

In order to ensure a correct working of screen printing rotary screens,the gauze or screen cylinder consisting of flexible material of therotary screen has to be tensioned in longitudinal direction, i.e. inaxial direction of the rotary screen. A possibility of longitudinallytensioning the rotary screens consists in that the frontal screenendpieces are axially supported in the screen holders and that thetensioning and releasing take place by adjusting at least one of thescreen holders on both sides in parallel to the rotary screen axis.There is the risk that upon releasing, i.e. upon replacing the screenholder in direction of the screen width, the screen holders are adjustedto a too large extent so that the screen cylinder is jolted andtherefore destroyed.

This shortcoming is avoided in that a means for limiting the movement ofthe screen holder is incorporated in the adjusting device of the movablescreen holder through which the movement of the screen holder is limitedto a predetermined extent upon releasing.

An embodiment of the invention is hereinafter described with referenceto the accompanying drawing'without being limited to it.

FIG. I is a schematic and diagrammatic view of a screen holder of arotary screen printing machine. FIG. I also represents a circuitdiagram.

FIG. 2 shows a detail of this circuit diagram.

FIG. 3 shows a section of an enlarged detail of FIG. 1.

One endpiece 2 of the rotary screen I is arranged in the screen holder 3of one machine side. The screen holder 3 is adjustable in parallel tothe rotary screen axis by means of the two threaded spindles 4 whosethreads are in mesh with corresponding nut thread elements (not shown inthe drawing) in the screen holder 3. The threaded spindles 4 are drivenby the shaft 5 which is driven by a motor M (shown in symbol). Uponadjusting the screen holder 3 in direction S the rotary screen 1 istensioned, the endpiece 2 of the rotary screen I being axially supportedby its disc 2 0n the parts 3' of the screen holder 3. Upon releasing,the screen holder 3 is adjusted in direction E.

The shaft 5 has the form of a screw 6 in the middle which works togetherwith a spiral wheel 7. A switching element 8 is arranged on theelongated shaft 7 of the spiral wheel or worm gear 7. The switchingelement 8 is connected with the shaft 7' by a slipping connection, e.g.by a fit or by an adjustable slipping clutch (Figure 3). Upon rotationof the shaft 7' the switching element is taken along up to a firm stop.This is the case upon tensioning the rotary screen 1 in direction S, theswitching element 8 first rotating with the shaft 7, but being stoppedon the stop 9, whereas the shaft 7 of the spiral wheel can continue itsrotation.

Upon releasing the rotary screen 1 in direction E the shaft 7 of thespiral wheel rotates in the other direction and takes along theswitching element 8 which is now removed from the stop 9 and rotatesinto the dash-lined position. At the end of this movement the switchingelement 8 pushes against the pushbutton 10 of the limit switch 10; thisis possible since the resistance the pushbutton l0 opposed to thepressing is smaller than the pulling moment of rotation conditioned bythe fit or slipping clutch between the shaft 7' and the pushbutton 8.Owing to the pressing of the pushbutton 8 the current supply to themotor M is interrupted, which stops the drive of the shaft 5 and themovement of the screen holder 3 in direction E. Thus the limit of themovement of the screen holder 3 is obtained upon release (direction E).

Figure 1 also shows a possible switching of the motor M. By actuatingthe switch 11 in direction S the motor M is set into movement indirection S for tensioning the rotary screen 1, and by actuating theswitch 11 III direction E for releasing or slackening the rotary screenin direction E. In the latter case the current is supplied to the motorM through the limit switch l0-see FIG. 2 and is interrupted, asdescribed, if the switching element 8 pushes the pushbutton 10' of thelimit switch 10.

The firm stop 9 is an eccentric piece and can be rotated in adjustablemanner; thus the field of traverse of the switching element 8 and theextent of the limit of the movement of the screen holder 3 can beadjusted upon release.

FIG. of a slipping clutch between the shaft 7' and the switching element8 can be seen in FIG. 3. On the shaft 7 which carries the spiral wheelor worm gear 7 in mesh with the screw 6, a jacket element 13 providedwith a circular flange 12 is arranged, not capable of rotation. Theswitch element 8 seated on the element 13 is pressed against thecircular flange 12 by means of the spring 14. Thus a frictionalconnection between the switching element 8 and the circular flange 12 isproduced owing to which the switching element is taken along uponrotating shaft 7 and rotating element 13 until the switching element 8is taken along by a firm stop (9 in FIG. 1).

What I claim is:

1. Apparatus on a rotary screen printing machine for longitudinallytensioning and slackening a rotary screen thereof comprising a machineframe, a pair of screen holders mounted on said frame, the ends of saidrotary screen being supported by said screen holders, means connected toone of said screen holders to make it movable and adjustable in parallelto the screen axis to cause tensioning and slackening of the screen, amotor operatively connected to said movable screen holder and positivelydriven to cause movement thereof for tensioning and slackening thescreen, and stopping means for limiting the movement of said movablescreen holder to a predetermined extend upon slackening, said stoppingmeans comprising a switching element with means supporting same andoperatively connecting it with said motor to be moved thereby, and alimit switch electrically connected to said motor, said switchingelement being engageable with said limit switch upon slackening thescreen to control said motor.

2. Apparatus as defined in claim 1 wherein the means for making saidscreen holder movable and adjustable include at least one shaftoperatively connected to said motor and to said one holder so that saidshaft is rotatable in the opposite directions to effect tensioning andslackening of the screen, said switching element being connected to saidshaft by means of a slipping connection.

3. Apparatus as defined in claim 2 wherein a stop member is mountedexternally of said shaft to engage the switching element as said elementis moved in a direction away from said switch, thereby limiting thefield of movement of said switching element, and said shaft of saidswitching element continues its rotation.

4. Apparatus as defined in claim 3 wherein said stop member iseccentrically pivotally mounted on a different shaft.

1. Apparatus on a rotary screen printing machine for longitudinallytensioning and slackening a rotary screen thereof comprising a machineframe, a pair of screen holders mounted on said frame, the ends of saidrotary screen being supported by said screen holders, means connected toone of said screen holders to make it movable and adjustable in parallelto the screen axis to cause tensioning and slackening of the screen, amotor operatively connected to said movable screen holder and positivelydriven to cause movement thereof for tensioning and slackening thescreen, and stopping means for limiting the movement of said movablescreen holder to a predetermined extend upon slackening, said stoppingmeans comprising a switching element with means supporting same andoperatively connecting it with said motor to be moved thereby, and alimit switch electrically connected to said motor, said switchingelement being engageable with said limit switch upon slackening thescreen to control said motor.
 2. Apparatus as defined in claim 1 whereinthe means for making said screen holder movable and adjustable includeat least one shaft operatively connected to said motor and to said oneholder so that said shaft is rotatable in the opposite directions toeffect tensioning and slackening of the screen, said switching elementbeing connected to said shaft by means of a slipping connection. 3.Apparatus as defined in claim 2 wherein a stop member is mountedexternally of said shaft to engage the switching element as said elementis moved in a direction away from said switch, thereby limiting thefield of movement of said switching element, and said shaft of saidswitching element continues its rotation.
 4. Apparatus as defined inclaim 3 wherein said stop member is eccentrically pivotally mounted on adifferent shaft.